Steel for sharpening knives.



No. 852,873. PATENTED MAY 7,1907.

J. B. DAVIDSON. 4

STEEL FOR SHARPENING KNIVES. APPLICATION FILED NOV. 6, 1905.

JOHN B. DAVIDSON, OF DERBY, CONNECTICUT.

STEEL FOR SHARPENING KNIVES.

Specification of Letters Patent Patented May '7, 1907.

Application filed November 6,1905. Serial No. 286,145.

To 1/7/21 whom, it may concern;

Be it known that I, JOHN B. DAVIDSON, a citizen of the United States, residing at Derby, in the county of New Haven and State of Connecticut, have invented a new and useful Improvement in Steels for Sharp ening Knives; and I do hereby declare the following, when taken in connection with the accompanying drawings and the letters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this specification, and represent, in

Figure 1 a broken view in side elevation of a sharpening steel made in accordance with my invention. Fig. 2 a greatly magnified broken view thereof in the nature of a dia gram to show the cross-sectional form of the ribs and grooves.

My invention relates to an improvement in steels, such as butchers steels, for sharpening knives, the object being to produce an article of superior effectiveness as a sharpening instrument.

YVith these ends in view, my invention consists in a steel for sharpening knives, the said steel being cross-sectionally round and its surface being formed with longitudinal ribs having convex outer faces and sharp overhanging cutting edges and separated from each other by corresponding intaglio grooves having undercut side walls producing the said overhanging cutting edges of the ribs.

As herein shown, the steel consists of a cross-sectionally round spindle 2 gradually tapering from base to tip and furnished with a suitable handle 3. The surface of the steel is formed with longitudinal ribs having slightly convex outer faces and overhanging cutting edges and separated from each other by longitudinal intaglio grooves having undercut side walls producing, as it were, the said overhanging cutting edges. The steel is produced by the following process: The steel is shaped, hardened, ground and polished. Its polished surface is then given a coat of varnish in which 150 to 200 longitudinal lines to the inch are subsequently scratched or cut. Thus made ready the steel is dipped in an acid bath which eats away the steel where exposed by the removal of the varnish, whereby intaglio grooves having undercut side walls are formed. The portions of the initial surface of the steel lying between the said grooves are protected against the action of the acid by the remaining varnish which itself is broken into longitudinal lines each one of which represents a rib in the finished steel. After the steel is removed from its acid bath to receive its handle. The faces of the ribs are slightly convex and are in fact part of the original rounded and polished surface of the steel. The overhanging corners of these ribs form sharp cutting edges and are produced by the action of the acid in eating away the steel up to the clean cuts in the varnish, undercutting, as it were, the side walls of the ribs. Both the said convex faces and cutting-edges are located in the plane of the initial body-curvature of the steel. I11 no case can the said edges stand above the original surface after the manner of the burr-like ridges produced by cutting the surface of a steel before it is hardened by means of a mechanical cutting instrumentality. This is objectionable as the cameo cutting edges thus formed are toned down paratory to hardening it. In heating the metal for the purpose of hardening it, it is discolored and must be polished which further dulls the edges produced by cutting before hardening. All these objections are avoided in acid-etched steels as produced by I claim As a new article of manufacture, a steel for sharpening knives, the said steel being crosssectionally round and its surface being formed with longitudinal ribs having convex outer faces and sharp overhanging cutting edges and separated from each other by longitudinal intaglio grooves having undercut side walls producing the said overhanging cutting edges of the ribs.

In testimony whereof, I have signed this specification in the presence of two subscribing witnesses.

JOHN B. DAVIDSON.

Witnesses:

GEO. C. ALLIs, I LEE Ross STUART.

by the subsequent heating of the metal pre-- the varnish is removed and the steel is ready 

